Stars have cores hot and dense enough to force atomic nuclei together, forming larger, heavier nuclei in a process known as fusion. In this process, the mass of the end products is slightly less than the mass of the initial atoms. But that “lost” mass doesn’t disappear — it’s converted to energy ... a lot of energy. So, can we harness this energy to power the world? George Zaidan investigates. This TED-Ed lesson was directed by Igor Ćorić, Artrake Studio, narrated by George Zaidan and the music is by Cem Misirlioglu and Brooks Ball.